In a cold region, there is a need to discharge, for example, snow accumulated on a roof in winter, to the ground efficiently via a drainpipe. In this regard, there is a problem that discharging water freezes inside the drainpipe or at an end portion on a downstream side of the drainpipe, whereby the drainpipe is blocked. If the drainpipe is blocked, the water is not discharged smoothly, whereby sometimes the water leaks indoors.
As a method of preventing freezing of discharging water inside the drainpipe, generally, a method of providing heat energy inside the drainpipe from outside, using a cord-shaped heater and the like is adopted (see Patent Document 1 for example). However, in such a method, a heater having a same height as a height of building is needed, whereby a running cost becomes large. In addition to this, a huge maintenance cost due to breakage and the like is required. Also, in a severely cold region, sometimes the drainpipe is installed indoors, whereby there is a large problem of installation space and design of the drainpipe.